MONDAY, Jan. 18, 2016 (HealthDay News) -- Mass shootings have prompted agony, anger and angst in the United States, causing citizens to ask why these events continue to happen and what can be done to stop them.

There are precious few answers to those questions, and there's at least one strong reason why: For nearly two decades, the U.S. government has declined to fund research into gun violence.

Without that funding, experts say, crucial questions on gun safety and gun violence have been left unanswered.

"People will tell you that we've got lots of laws regarding guns, and they're just not being enforced," said Dr. Georges Benjamin, executive director of the American Public Health Association. "In my mind, that argument falls short, because we're not doing the research to evaluate how those laws are doing, to see how to best enforce them or how they should be tweaked if there's a hole in those laws."

Other important topics that have been left unstudied include design changes that could make guns safer, the number of nonfatal firearm injuries that occur each year, and the effectiveness of safety training for firearms, experts said.

"There are so many things we just don't know anything about," said David Hemenway, director of the Harvard Injury Control Research Center in Boston. "Any gun-related topic you list, there are huge gaps in our knowledge."

President Barack Obama's recent executive orders issued on firearms will do little to resolve this problem, Hemenway added. Obama's orders focused on improved background checks and effective enforcement of existing gun laws, but only contained a single mention of research to improve gun safety technology.

"Congress controls the funding and they recently eliminated funds in the President's budget for the CDC (Centers for Disease Control and Prevention) for gun research," Hemenway said.

What many Americans might not know, Benjamin said, is that the trillion-dollar spending bill passed by Congress and signed by Obama in December retained a ban on firearms research that dates to the 1990s.

Elected officials renewed the ban despite then-recent mass shootings in San Bernardino, Calif., and Colorado Springs, Colo., and an outcry from public health officials.

A Dec. 16 editorial in the New England Journal of Medicine noted that more than 33,000 people died from gunshot injuries and more than 84,000 were wounded in 2013, according to CDC statistics.

"If any other public health menace were consistently killing and maiming so many Americans, without research, recommendations, and action by the CDC, the public would be outraged," the journal editorial said.

The research freeze also continued over the objections of the politician it's named after, former U.S. Rep. Jay Dickey, a Republican from Arkansas. In 1998, what became known as the Dickey Amendment effectively blocked the CDC from conducting future research into gun violence.

But Dickey now thinks the nation shouldn't have to choose between reducing gun-violence injuries and safeguarding gun ownership. And he very publicly said so in a Dec. 1 letter to the House Democrats' task force on gun violence prevention.

"I took part in cutting off gun violence research dollars at the federal level because of what was considered a misapplication of the dollars by the CDC," Dickey wrote. "I have recently expressed my regrets that we didn't continue that research with the provision that nothing shall be done in this project to infringe the rights of gun ownership as guaranteed by the U.S. Constitution in the Second Amendment."

Dickey believes research into the causes of gun violence can save lives just as collision research by highway officials has done. Their investigation didn't result in the elimination of automobiles, but led to the placement of concrete barriers that keep drivers from veering into oncoming traffic.

"In the same way, scientific research should help answer how we can best reduce gun violence," Dickey wrote. "Doing nothing is no longer an acceptable solution."

The Dickey Amendment and the defunding of firearms research have profoundly affected the nation's knowledge of gun violence, turning many talented scientists away from the topic, said Daniel Webster, director of the Johns Hopkins Center for Gun Policy and Research.

"Scientists get invested in how they're going to spend their careers, and they need funding to support those careers," Webster said. "If the federal government signaled that yes, gun violence is a big problem, we're going to have a long-term investment in better understanding that problem and what we can do to prevent it, you'd have a lot more scientists involved and we'd know a lot more than we do now," he explained.

"Right now there's only a handful of researchers who have dedicated a significant portion of their careers on this problem, which is just mind-boggling when you think about where it ranks as a public health problem, not to mention a broader social concern," Webster added.

Some research has continued, thanks to private funding, Webster said. He cited a recent study that showed mandatory background checks for firearms purchases can save many lives by reducing the number of homicides and suicides, and also by keeping guns out of the hands of criminals.

But Webster, Benjamin and Hemenway rattled off a long list of research topics that have not been pursued, including:

Whether firearms as a consumer product can be made safer. "What should the trigger pull be on a firearm so that a kid can't use it?" Benjamin said. "Is there a way to create a firearm so it can't be altered beyond the purpose for which the gun was made?"

The extent of nonfatal gunshot wounds. "Our systems are not really set up to track these events," Webster said, adding that an estimated three or four nonfatal injuries are believed to occur for every gun-related fatality.

The effectiveness of firearms training programs. "We know virtually nothing about gun training," Hemenway said. "What is being taught? Can we make it better? Should there be mandatory gun training?"

The role of the underground firearms market. "We need to know more about where those guns are and how individuals most prone to use those guns inappropriately might access them," Webster said.

The best ways to prevent gun-related suicides. "Almost two-thirds of all fatalities with guns in the United States are suicides," Webster said. "There's been very little research examining what's the most effective way to separate an individual in crisis from a gun."

These questions and more could be answered with a push from the federal government, Webster said.

He compared gun research to that conducted on motor vehicle safety and HIV. "You had large and long-term investment of the federal government," Webster said. "They recognized these as big problems that kill lots of Americans."

Obama's executive order regarding research on gun safety technology could prove a first step in that direction, Hemenway noted. The president directed the departments of Defense, Justice and Homeland Security to conduct or sponsor research into technology that would make guns less able to discharge accidentally or be stolen.

"A few years ago I wrote a book entitled 'While We Were Sleeping: Success Stories in Injury and Violence Prevention.' It provided 64 documented successes where injury or violence has been successfully reduced," Hemenway wrote in an editorial on Obama's announcement. "The vast majority of successes entailed changing technology rather than changing human behavior. The former is much easier to accomplish and more cost-effective."

From such investment, people with HIV, for instance, now live longer and it costs less to care for them. And, graduated driver's licenses have saved the lives of countless young drivers by preventing them from driving at night and with other teens in the car, he said.

"If funding is re-established, things would not change overnight," Webster said. "But goodness, this is a long-term thing. The longer we wait, the more deaths will accumulate."